Heat exchanger assembly for aircraft ecs

ABSTRACT

An aircraft environmental conditioning system is disclosed that includes an air cycle system for conditioning a flow of hot compressed air by reducing its temperature and pressure. The air cycle system includes a heat exchanger having a heat rejection side in fluid communication with the airflow and a heat absorption side in fluid communication with external unconditioned air. The system also includes an airflow path from an external air inlet to the heat absorption side of the heat exchanger. A centrifugal separator is disposed in the airflow path, and includes a tubular body portion having an inlet that receives airflow, a deflector in the tubular body portion that imparts a vortex motion to airflow in the tubular body portion, and an outlet portion that includes a clean air outlet in fluid communication with the heat absorption side of the heat exchanger and a scavenge air outlet for removing particulate matter.

BACKGROUND OF THE INVENTION

This invention relates to environmental air conditioning systems (ECS), and more specifically to air cycle environmental air conditioning systems such as used on aircraft.

Aircraft that fly at altitudes above that at which ambient air is suitable for crew, passengers, cargo, or equipment are often equipped with air cycle environmental air conditioning systems to provide pressurized conditioned air. These air conditioning systems typically utilize a pressurized air bleed from a turbine fan engine or an auxiliary power unit (APU), or in some cases from an electrically-powered compressor as a source of compressed air that flows along an airflow path through the air cycle environmental air conditioning system to produce conditioned air for the cockpit and passenger cabin or other pressurized areas of the aircraft. The compressed air that is fed into these systems is typically at a temperature and pressure far in excess of the normal temperature and pressure for conditioned air to be supplied to the cockpit and passenger cabin, so it must be expanded and cooled by the air conditioning system before it can be discharged as conditioned air. Aviation air cycle environmental conditioning systems typically process the bleed air through multiple cycles of cooling/pressure reduction and compression/heating. Cooling and pressure reduction is accomplished with heat exchangers (including condensers) and with turbines (which also extract work from the bleed air), while compression/heating is accomplished with compressors and reheaters. Many systems include at least one heat exchanger that utilizes external air to cool the bleed air.

Air cycle-based aviation ECS systems are required to operate under a variety of conditions. Some of these conditions can involve exposure to airborne particulates, which can result in the accumulation of particulate debris on and around the heat absorption side of heat exchangers that use external air to absorb heat from the bleed air. Continued accumulation of such debris can ultimately lead to partial to complete or near-complete airflow blockage on the heat absorption side of the heat exchanger, which can result in reduced cooling performance, fan surge, broken fan blades, and system failure. Fan blade breakage can also involve failed journal bearings, turbine rotor rubs, and smoke events in the cabin.

BRIEF DESCRIPTION OF THE INVENTION

According to an aspect of the invention, an aircraft environmental conditioning system comprises an air cycle conditioning system for conditioning an airflow comprising hot compressed air by reducing its temperature and pressure. The air cycle conditioning system includes a heat exchanger having a heat rejection side in fluid communication with the airflow and a heat absorption side in fluid communication with external unconditioned air. The system also includes a heat exchanger assembly comprising an external air inlet and a first flow path from the external air inlet to the heat absorption side of the heat exchanger and from the heat absorption side of the heat exchanger to an external air exhaust outlet. A particulate separator is disposed in the first flow path between the external air inlet and the heat exchanger, and is movable between a deployed position in the first flow path and a stand-by position not in the first flow path.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic representation of an exemplary heat exchanger assembly in an environmental condition system as described herein;

FIG. 2 is a schematic representation of a centrifugal separator as described herein;

FIG. 3 is a schematic representation of a centrifugal separator disposed in an air flow path of a heat exchanger assembly;

FIG. 4 is a schematic representation of the centrifugal separator of FIG. 3 stowed in a stand-by position out of the air flow path; and

FIG. 5 is a schematic representation of a centrifugal separator disposed in a first air flow path of a heat exchanger assembly that also has a second air flow path that bypasses the centrifugal separator.

DETAILED DESCRIPTION OF THE INVENTION

Turning now to FIG. 1, an air cycle conditioning system for use as an aircraft environmental conditioning system (ECS) includes a heat exchanger assembly having an inlet conduit 12 with ram inlet 13 that directs external air 14 to the heat absorption side of a heat exchanger 16 such as a tube and fin heat exchanger, a plate fin heat exchanger, or a minichannel heat exchanger. Hot compressed bleed air from an engine or auxiliary power unit (APU) 18 flows into the heat rejection side of the heat exchanger 16 through bleed air conduit 20 where it is cooled by rejecting heat to the external air 14 on the heat absorption side of the heat exchanger 16. The cooled bleed air exits the heat exchanger 16 through conduit 22 and is delivered to the remainder of the air cycle conditioning system components 24. The remainder of the air cycle conditioning system components 24 can include, but are not limited to compressors for increasing pressure and temperature, turbines for reducing pressure and temperature and extracting work, condensers/reheaters for removing moisture, and other components known in the art. The details of such other components and their arrangement and operation in an aircraft environmental conditioning system are well known, and do not require further description here. The heat exchanger assembly can also include a fan 26 to assist the flow of external inlet air along its flow path through the assembly under conditions when the aircraft is stopped or is not moving at velocities sufficient to obtain the desired airflow through the ram inlet 12. A secondary inlet 25 can also be opened and used instead of ram inlet 13 for external air 14 to enter when the aircraft is stopped or is not moving at velocities sufficient to obtain the desired airflow through the ram inlet 12. After absorbing heat from the ECS system's bleed air, the external air 14 exits the heat exchanger assembly through outlet 28. The environmental conditioning system depicted in FIG. 1 also includes a controller 27 (e.g., an electronic control unit or ECU) operatively connected to the engine or APU 18, the air cycle conditioning components 24, and the heat exchanger assembly. The operation of the controller 27 is further described below.

FIG. 1 also depicts a particulate separator 30 along the air flow path between the ram inlet 12 and the heat exchanger 16. In some embodiments, the particulate separator 30 is configured to remove particles of a size range that tend to cause blockages in the heat exchanger 16, e.g., particle sizes from 4 μm to 3 mm. The particulate separator 30 is movable between a deployed position in the air flow path and a stand-by position not in the air flow path. The particulate separator can be a screen, mesh, or filter, or can be a centrifugal separator or an array or bank of centrifugal separators. A single centrifugal separator 30′ is schematically depicted in FIG. 2. As shown in FIG. 2, the centrifugal separator 30′ comprises a tubular body portion 34 having an inlet 36. Particulate-containing air 38 enters the tubular body portion 34 through inlet 36, and encounters a deflector 38 that imparts a whirling or vortex motion to the air as it travels through the tubular body portion 34. Centrifugal force from this motion causes particulates suspended in the air flow to be directed toward the inside walls of tubular body portion 34. Outlet portion 40 has a receiving portion 42 having a narrower internal diameter than that of tubular body portion 34 such that when the airflow encounters the outlet portion 40, the particulate-laden air 44 near the inner walls of tubular body portion 34 exits through scavenge air outlet 46 while the relatively cleaner air 48 farther away from the inner walls of tubular body portion 34 exits through clean air outlet 50.

FIGS. 3-5 depict schematic representations of a portion of the heat exchanger assembly 10 depicting a two-row array 30 of centrifugal separators with greater details regarding configuration and airflow path, and the same reference numbers from FIGS. 1 and 2 are used to identify like components in FIGS. 3-5. As shown in FIG. 3, external inlet airflow 14 flows through conduit 52 and into the centrifugal separator inlets 36. A whirling or vortex motion is imparted to the airflow by deflectors 38 causing particulate-laden air 44 to exit from the scavenge air outlets 46 from where it is through the centrifugal separator array exhaust port 54. A conduit (not shown) can carry the scavenge air 46 to an external exhaust (not shown) from the heat exchanger assembly. The clean air 48 exiting the outlets is delivered to the heat absorption side of heat exchanger 16 where it absorbs heat rejected from bleed air flowing through heat exchanger tubes 16′. The air 56 exiting from the heat absorption side of heat exchanger 16 is then discharged through outlet 28 (FIG. 1).

The centrifugal separator(s) are movable between a deployed position in the external inlet air flow path (i.e., first flow path) and a stand-by position not in the external inlet air flow path. FIGS. 3 and 4 together illustrate an embodiment where a centrifugal separator array is movable between a deployed position (FIG. 3) and a stand-by position (FIG. 4). The centrifugal separator array 30 can be moved between the positions by any known means (not shown), such as electromechanical actuators or hydraulic actuators, the details of which are known in the art and do not require further explanation. As shown in FIG. 4, the centrifugal separator array 30 is in a stand-by position in the space between the conduit 52 and the heat exchanger assembly housing 32. The centrifugal separator array 30 is deployed through an opening 53 in conduit 52 to its deployed position as shown in FIG. 3. In some embodiments, the centrifugal separator or centrifugal separator array is configured to, or is disposed in a housing configured to align and seal with the conduit 52. As shown in FIG. 3, in the deployed position, the centrifugal separator array wall surfaces 58 and 60 each align with and seal against the conduit 52 to prevent external inlet air 14 from bypassing the centrifugal separator array 30. As shown in FIG. 4, in the stand-by position, the 4, the centrifugal separator array wall surface 58 aligns with and seals against the conduit 52 to close up the opening 53 in conduit 52 so that external inlet air 14 is directed through conduit 52 to the heat absorption side of heat exchanger 16.

In some embodiments, the heat exchanger assembly further comprises a second flow path, without a centrifugal separator disposed therein, connecting the external air inlet to the heat absorption side of the heat exchanger. An example of such a configuration is depicted in FIG. 5. As shown in FIG. 5, a door 62 is movable between first and second positions 62′ and 62″, respectively. In the first position 62′, the door forces external inlet air along first flow path 14′ to the centrifugal separator array 30 where it operates in similar fashion as shown in FIG. 3. In the second position 62″, the door forces external inlet air along second flow path 14″ where it travels directly to the heat absorption side of heat exchanger 16, bypassing the centrifugal separator array 30.

The invention allows, but does not require, that centrifugal separators can be controllably interposed in an external inlet air stream for an aircraft ECS heat exchanger. The exercise of such control can provide beneficial technical effects such as eliminating or minimizing pressure drop by excluding the centrifugal separators from the air flow path under conditions where lower airborne particulate levels are expected, and also utilizing the centrifugal separators to remove or reduce airborne particulates under conditions where greater airborne particulate levels are expected. Accordingly, in some embodiments such as shown in FIG. 1, a controller 27 is operationally connected to the heat exchanger assembly, and optionally to other system components such as engine or APU 18 or air cycle conditioning system components 24. The control connections depicted are exemplary and schematic in nature, and it is understood that connections can be established in a variety of configurations as is known in the art, such as through direct electronic connections or through a distributed or centralized control network. In the exemplary embodiments shown in FIGS. 3-5, the controller 27 can be configured to move the centrifugal separator array 30 between the deployed position (FIG. 3) and the stand-by position (FIG. 4), or to move the door 62 between positions 62′ and 62″ (FIG. 5).

In some embodiments, the controller 27 (FIG. 1) can move the centrifugal separator array 30 or the door 62 in response to manually entered commands from operating personnel. In some embodiments, the controller 27 can move the centrifugal separator array 30 or the door 62 in response to a predetermined condition. In some embodiments, the predetermined condition is based on an expected likelihood of encountering higher levels of airborne particulates. In some embodiments, the predetermined condition is based on the altitude of the aircraft relative to the ground. In some embodiments, the precondition is based on the operational state of a fan disposed in the air flow path. In some embodiments, the precondition specifies that air from the external air inlet is directed through the centrifugal separator (e.g., FIG. 3 or door 62 in position 62′ in FIG. 4) if the aircraft is within proximity to or on the ground, and is not directed through the centrifugal separator (e.g., FIG. 4 or door 62 in position 62″ in FIG. 4) if the aircraft is at altitude. In some embodiments, air from the external air inlet is directed through the centrifugal separator (e.g., FIG. 3 or door 62 in position 62′ in FIG. 4) if the fan is operating, is not directed through the centrifugal separator when the fan is not operating (e.g., FIG. 4 or door 62 in position 62″ in FIG. 4).

While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims. 

1. An aircraft environmental conditioning system, comprising an air cycle conditioning system for conditioning an airflow comprising hot compressed air by reducing its temperature and pressure, the air cycle conditioning system including a heat exchanger having a heat rejection side in fluid communication with said airflow and a heat absorption side in fluid communication with external unconditioned air; a heat exchanger assembly comprising an external air inlet and a first flow path from the external air inlet to the heat absorption side of the heat exchanger and from the heat absorption side of the heat exchanger to an external air exhaust outlet; a particulate separator disposed along the first flow path between the external air inlet and the heat exchanger, the particulate separator being movable between a deployed position in the first flow path and a stand-by position not in the first flow path.
 2. The aircraft environmental conditioning system of claim 1, wherein the heat exchanger assembly further comprises a fan disposed in the first flow path.
 3. The aircraft environmental conditioning system of claim 1, wherein the particulate separator is a screen or mesh.
 4. The aircraft environmental conditioning system of claim 1, wherein the particulate separator is a centrifugal separator comprising a tubular body portion having an inlet that receives external air from the external air inlet, a deflector in the tubular body portion that imparts a vortex motion to air flow in the tubular body portion, and an outlet portion that comprises a clean air outlet in fluid communication with the heat absorption side of the heat exchanger and a scavenge air outlet for removing particulate matter.
 5. The aircraft environmental conditioning system of claim 4, comprising a plurality of said centrifugal separators disposed along the first flow path.
 6. The aircraft environmental conditioning system of claim 1, wherein the particulate separator is configured to, or is disposed in a housing configured to align and seal with a conduit along the first flow path, thereby directing the external air flow along the first path into the tubular body inlet.
 7. The aircraft environmental conditioning system of claim 1, further comprising a controller configured to direct the particulate separator to move between the deployed position and the stand-by position.
 8. The aircraft environmental conditioning system of claim 7, wherein the external air inlet comprises a ram external air inlet and a secondary external air inlet, and the controller is configured to direct air from the ram air inlet along the first flow path when the centrifugal separator is in the stand-by position, and is configured to deploy the particulate separator when the secondary external air inlet is open.
 9. The aircraft environmental conditioning system of claim 7, wherein the controller is configured to deploy the particulate separator if the aircraft is on or within proximity to the ground or if the fan is operating.
 10. The aircraft environmental conditioning system of claim 1, wherein the heat exchanger assembly further comprises a second flow path, without a particulate separator disposed therein, connecting the external air inlet to the heat absorption side of the heat exchanger.
 11. The aircraft environmental conditioning system of claim 10, wherein the external air inlet comprises a ram external air inlet and a secondary external air inlet, the first flow path is along a path from the secondary external air inlet to the particulate separator to the heat absorption side of the heat exchanger, and the second flow path is along a path from the ram external air inlet to the heat absorption side of the heat exchanger.
 12. The aircraft environmental conditioning system of claim 10, further comprising a controller configured to direct air from the external air inlet between the first flow path and the second flow path.
 13. The aircraft environmental conditioning system of claim 12, wherein the controller is configured to direct air from the external air inlet to the first flow path when the aircraft is on or proximate to the ground or the fan is operating, and is configured to direct air from the external air inlet to the second flow path when the aircraft is in flying at altitude or the fan is not operating.
 14. The aircraft environmental conditioning system of any of claims 1-13, wherein the particulate separation device is configured to separate particles of 4 μm to 3 mm from air in the first flow path. 